/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.loader;

import org.apache.catalina.LifecycleException;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.compat.JreCompat;

import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * Parallel class loading implementation of WebappClassLoaderBase. Parallel
 * class loading is only available when using a Java 7+ JRE.
 */
public class ParallelWebappClassLoader extends WebappClassLoaderBase {

	private static final Log log = LogFactory.getLog(ParallelWebappClassLoader.class);

	static {
		try {
			if (JreCompat.isJre7Available()) {
				// parallel class loading capable
				final Method registerParallel =
						ClassLoader.class.getDeclaredMethod("registerAsParallelCapable");
				AccessController.doPrivileged(new PrivilegedAction<Object>() {
					@Override
					public Object run() {
						registerParallel.setAccessible(true);
						return null;
					}
				});
				Boolean result = (Boolean) registerParallel.invoke(null);
				if (!result.booleanValue()) {
					log.warn(sm.getString("webappClassLoaderParallel.registrationFailed"));
				}
			}
		} catch (Exception e) {
			// ignore
		}
	}


	public ParallelWebappClassLoader() {
		super();
	}

	public ParallelWebappClassLoader(ClassLoader parent) {
		super(parent);
	}

	/**
	 * Returns a copy of this class loader without any class file
	 * transformers. This is a tool often used by Java Persistence API
	 * providers to inspect entity classes in the absence of any
	 * instrumentation, something that can't be guaranteed within the
	 * context of a {@link java.lang.instrument.ClassFileTransformer}'s
	 * {@link java.lang.instrument.ClassFileTransformer#transform(ClassLoader,
	 * String, Class, java.security.ProtectionDomain, byte[]) transform} method.
	 * <p>
	 * The returned class loader's resource cache will have been cleared
	 * so that classes already instrumented will not be retained or
	 * returned.
	 *
	 * @return the transformer-free copy of this class loader.
	 */
	@Override
	public ParallelWebappClassLoader copyWithoutTransformers() {

		ParallelWebappClassLoader result = new ParallelWebappClassLoader(getParent());

		super.copyStateWithoutTransformers(result);

		try {
			result.start();
		} catch (LifecycleException e) {
			throw new IllegalStateException(e);
		}

		return result;
	}
}